Scalability

This question was set here on purpose due to the fact that many people still get confused about scalability and High Availability, even though both topics are quite different from one another. You'll be using High Availability to keep your service available as much as possible during time, thus improving the user experience and also the availability of your service. You'll however, implement scalability to ensure that the service is responding to the service requests (or demand) and therefore, being provided efficiently and in a timely fashion. Don't forget that scalability is used not only to add resources to a service, but also to reduce the service resources, depending on the need and the scope of that same service.

You'll usually start the Orchestrator architecture with a single server deployment to see how it goes and how you can answer the automation requests you'll find. It will be during the technology lifetime that you'll see the demand...